A German zoologist, Ernst Haeckel, coined and defined a new branch of biology, "Oekologie," in 1866 (Egerton 2013). In the later 1800s, four ecological sciences emerged: (terrestrial) plant ecology, (terrestrial) animal ecology, limnology, and marine biology. Plant ecology evolved out of phytogeography and physiology (Billings 1985:5-6), to which was added during the 1890s investigations of plant communities and vegetation succession. Physiology was important, but played a relatively passive role: its significance often depending on how well phytogeographers understood it. European botanists and publications led the way. Phytopathology during the 1800s is discussed in part 44 (Egerton 2012) and omitted here. For phytopathology during the early 1900s, see G. C. Ainsworth, Introduction to the History of Plant Pathology (1981) and C. L. Campbell et al., The Formative Years of Plant Pathology in the United States (1999:225-339). The history of aquatic plant ecology is part of limnology and marine ecology and will be discussed in parts 50 and 51. The ecology of lichens is deferred to part 52 on the history of symbiosis studies. After these exclusions, the remaining plant ecology, about 1870 to mid-1920s, is still vast in scope and detail, and surveys by